Nomogram development

Nomograms were developed using the training cohort. Follow-up length was defined as the time from diagnosis to failure or censoring. Observed OS and CSS times were estimated by median follow-up length. Cox's proportional hazards regression model was conducted by the R software “cph” and “step” commands. Age, race, sex, tumor site, tumor grade, surgery, radiotherapy and TNM stage were used as the starting factor combination. The Akaike Information Criterion (AIC) [30] was obtained via the above-mentioned commands, and the combinations of factors with the smallest number of AIC were used as the models to develop nomograms predicting five- and eight-year HNSCC patient OS [31]. Independent CSS factors obtained via competing risks model were used to develop nomograms predicting five- and eight-year HNSCC patient CSS. R version 3.2.4 software was used to develop nomograms.